1. Field of the Invention
The present invention relates to telecommunications and, more particularly, to delivery of telecommunications services via local loop telephone lines to customer premises.
2. Description of Related Art
A typical telecommunications network includes telephone units interconnected to each other via switching equipment and transmission lines owned and operated by local exchange carriers (LECs) and interexchange carriers (IXCs). Conventionally, a LEC will own and operate a “central office” switching center that includes a switch connected with telephone lines extending out to various customer premises, such as homes and companies. The switch will then be coupled by signaling and voice trunks with the public switched telephone network (PSTN), i.e., with other switches and network elements that provide connectivity with other customer premises.
When a call is placed from a given customer premises to a dialed number, the dialed number passes along the telephone line to the central office, and the switch then sets up the call to the dialed number. If the dialed number is a local number also served by the switch, then the switch simply sets up and routes the call over a telephone line extending out to the called premises. Alternatively, if the dialed number is served by a remote central office (owned by the same or by another LEC), then the switch sets up and routes the call to the remote central office (possibly via an IXC network), and the remote central office sets up and routes the call over a telephone line to the called premises.
The telephone line that extends between a given customer premises and the telephone company switch could take various forms and can range in degree of complexity. By way of example, the telephone line could be a twisted pair of copper wires that extends all the way from the customer premises to the switch. As another example, the telephone line could extend as a pair of copper wires from the customer premises to a digital concentrator and then as a digitized channel on a cable from the concentrator to the switch.
And as still another example, the telephone line could extend as a digitized channel on coaxial cable from the customer premises to a cable company's “head-end” and then from the head-end to a cable “point of presence” that includes a telephone switch. In that case, the cable company could function as a telephone company, and its point of presence could function as a central office, with the telephone switch at the point of presence providing connectivity between telephone lines and the PSTN. Other examples of telephone lines are possible as well.
At the customer premises, a telephone line connects with a junction box that is wired to telephone units such as telephones, answering machines, fax machines and modems. At the telephone company central office, on the other hand, the telephone line typically extends through a main distribution frame (MDF) and then passes to the switch. Because the telephone line establishes a circuit connection between the customer premises and the telephone company switch, the telephone line is commonly referred to as a “local loop” or “subscriber loop.” It may also be referred to as a “local loop telephone line.”
In order to provide basic telephone functions such as tone generation, digit-detection and ringing, a telephone company will tie each telephone line to a respective “subscriber line interface circuit” (SLIC). The SLIC could sit at any point along the telephone line, usually at the central office. For instance each telephone line can connect with a dedicated line card at the central office, and the line card can include SLIC functionality and can couple the telephone line with the switch. Alternatively, SLIC functions can be provided by the switch itself.
Recognizing the need for competition in the local phone market, the United States Federal Communications Commission (FCC) has mandated that LECs who own local switching centers (known as incumbent LECs or “ILECs”) must make certain network equipment available for lease by competitive local exchange carriers (CLECs). In one respect (referred to as “unbundled network equipment”), for instance, the mandate requires ILECs to make unbundled portions of their network infrastructure, such as individual loops and switching functions, available for lease by CLECs.
Depending on the number of customers served in a given region, it is often not economically feasible for a CLEC to install its own local loop telephone lines or switching equipment. With the benefit of the FCC's mandate, however, a CLEC can now readily offer local telephone service to customers without having to install local loops or switches to serve those customers. Rather, the CLEC can simply lease just the ILEC infrastructure that it needs in order to serve those customers who sign up for the CLEC's service, and the CLEC need not lease other portions of the ILEC's infrastructure. From the customer's perspective, the CLEC would be providing local phone service. But in reality, the ILEC's local loop lines and switch may be providing connectivity with the PSTN.
Although the FCC's mandate opens the door to greater competition in the local phone market, a CLEC wishing to provide local telephone services must still lease a significant portion of the ILEC's network infrastructure, including both the local loop and the switching infrastructure, for each customer that the CLEC will serve.